Sliding component and method for manufacturing the same

ABSTRACT

A bearing is manufactured by filling iron-based material powder and copper-based material powder in a filling portion of a mold, compacting those material powder so as to form a green compact, and then sintering the green compact. The copper-based material powder contains flat powder particles, the flat powder particles having a large aspect ratio than particles of the iron-based material powder. The coppers-based powder particles segregate on a sliding surface by vibration. The sliding surface of a bearing is covered with copper, and a ratio of iron increases from the sliding surface toward the inside. Since a rotation shaft slides on the sliding surface covered with copper, a frictional coefficient between the rotation shaft and the sliding surface is reduced, thus enabling a smooth rotation thereof. Simultaneously the usage of iron imparts predetermined strength and durability.

CROSS-REFERENCE TO PRIOR APPLICATION

This is a U.S. National Phase application under 35 U.S.C. §371 ofInternational Patent Application No. PCT/JP2003/009862 filed Aug. 4,2003, and claims the benefit of Japanese Patent Application No.2002-249692 filed Aug. 28, 2002 both of which are incorporated byreference herein. The International Application was published inJapanese on Mar. 11, 2004 as WO 2004/020129 A1 under PCT Article 21(2).

BACKGOUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sliding component such as a bearingor the like and a method for manufacturing the same.

2. Description of the Related Art

Typically, a bearing which supports a rotation shaft is one of therepresentatives of this kind of sliding components, which ismanufactured by a well-known method including the steps of compactingmaterial powders mainly composed of metallic materials so as to form agreen compact; and then sintering this green compact to thereby obtainan oil impregnated sintered bearing as used popularly.

Oil impregnated sintered bearings are formed by using iron-based orcopper-based material powder. If iron-based material powder is used,bearings with superior strength can be obtained. However, since aniron-based material such as steel is generally used for a rotationshaft, frictional resistance becomes large due to the same types ofmaterials being used for both of the bearing and the rotation shaft sothat a fused wear is very likely to occur, thus impairing durabilitythereof. On the contrary, if copper-based material powder is used,frictional resistance between the bearing and the rotation shaft becomessignificantly small, but a wear of the bearing becomes large, and thusdurability thereof is also impaired.

Like the general bearing products, oil impregnated bearing products havealso been developed in order to provide ones with improved durabilityand reduced frictional resistance. For instance, oil impregnatedsintered bearings using iron powders plated with copper or copper alloyas material powder are known. According to the bearings, because theyare made up of composite materials consisting of copper and iron, theoil impregnated sintered bearings not only can reduce frictionalresistance thereof but also can improve durability thereof compared toconventional ones.

Also, Japanese Examined Patent Publication No. 63-24041 proposes amethod for manufacturing a sintered component, including the steps ofadding a material forming the second phase to material powders forming amatrix so as to form a sintered mechanical component, wherein the secondphase forming material is in the form of foil-like powder, of which theaverage particle size “a” is smaller than half of the average particlesize “r” of the material powder (i.e., 2a<r). According to this method,a surface of the sintered component can be effectively covered with thesecond phase element of notably little additive amount, compared to byconventional techniques, and thus the sintered component whose surfaceis copper-rich can be obtained when copper in the form of foil-likepowder is added to iron-based material powder.

Recently, in addition to requirements for wear proofness and durability,a further requirement for noiselessness has been raised to the bearingsor the like. For instance, noiselessness in initiating the rotation of arotation shaft in such a low-temperature state as low as minus 40degrees centigrade is required, which, however, has been difficult forthe conventional ones to meet.

The present invention has been made to solve the above-describedproblems, and it is accordingly an object thereof to provide a slidingcomponent which can accomplish the reduction of frictional resistancethereof and the improvement of durability thereof, as well as theprevention of noises when initiating the rotation of a rotation shaft.Another object thereof is to provide a method for manufacturing thesame.

SUMMARY OF THE INVENTION

In order to attain the above objects, according to a first aspect of thepresent invention, there is provided a sliding component formed by:filling an iron-based material powder and a copper-based material powderin a filling portion of a mold; compacting the iron- and copper-basedmaterial powders so as to form a green compact; and sintering the greencompact, wherein: the copper-based material powder contains aflat-particle powder (hereinafter flat powder particles) of copper orcopper alloy; an average value of maximum projected areas of the flatpowder particles is larger than that of maximum projected areas of theiron-based material powder particles; and copper is allowed to segregateon one surface of the sliding component.

According to the above-described structure, the flat powder particles ofcopper or copper alloy are employed, and filled into the filling portionof the mold together with other material powder(s), allowing the flatpowder particles to segregate on the surface of the sliding component,using vibration, electrostatic force, magnetic force or the like,whereby the sliding component thus obtained can have its surface coveredwith copper, generating a concentration gradient in which thecopper-to-iron ratio thereof decreases from the surface of the slidingcomponent toward the inside thereof while increasing the ratio of iron.Therefore, in a case that the bearing is formed from this slidingcomponent, a rotation body is allowed to slide on the surface coveredwith copper with a reduced frictional coefficient between the rotationbody and the surface, and thus a smooth rotation can be realized, whileensuring predetermined strength and durability by virtue of iron.Moreover, according to the above-described structure, even though thesurface on which the rotation body slides wears, the sliding portionscan maintain superior durability since copper is contained at thepredetermined ratios under the worn surface.

Alternatively, in the above-described sliding component, the foregoingflat powder particles may have a larger aspect ratio than those of theiron-based material powder.

Moreover, in the above-described sliding component, the surface coverageof copper in the sliding portion of the sliding component may be greaterthan or equal to 60%. Thus, the frictional resistance between thesliding surfaces can be dramatically decreased. More preferably, suchsurface coverage of copper may be greater than or equal to 90%.

Further, the aforesaid sliding portion of the sliding component of thepresent invention may be a sliding surface of a cylindrical shape, thusproviding a bearing rotationally supporting the rotation body by thissliding surface.

In order to attain the above objects, there is provided a method formanufacturing a sliding component according to another aspect of thepresent invention, including the steps of filling an iron-based materialpowder and a copper-based material powder in a filling portion of amold; compacting the iron- and copper-based material powders so as toform a green compact; and sintering the green compact, wherein thecopper-based material powder contains flat powder particles of copper orcopper alloy; an average value of maximum projected areas of the flatpowder particles is larger than that of maximum projected areas of theparticles of the iron-based material powder; and the flat powderparticles in the filling portion are allowed to segregate on the surfaceof the green compact.

According to the above-described structure, the flat powder particles ofcopper or copper alloy are employed, and then filled into the fillingportion of the mold together with other material powder(s), allowing theflat powder particles to segregate on the surface of the slidingcomponent, using vibration, electrostatic force, magnetic force or thelike, whereby the obtained sliding component is covered with copper,generating a concentration gradient in which the copper-to-iron ratiodecreases from the surface of the sliding component toward the insidethereof while increasing the ratio of iron, and thus the slidingcomponent can have reduced frictional coefficient as well as superiordurability.

Alternatively, in the above-described method, the flat powder particlesmay have a larger aspect ratio than the iron-based material powder.Thus, the flat powder particles are allowed to segregate on the surfaceof the green compact by vibration.

Moreover, in the above-described method, the aspect ratio of the flatpowder particles may be greater than or equal to 10. When vibration isapplied, the flat powder particles are allowed to successfully segregateon the surface, thus obtaining the sliding component of which the copperconcentration is getting higher toward the surface. More preferably, theaspect ratio of the flat powder particles may be in the range of from 20to 50.

Further, in the above-described method, the proportion of the flatpowder particles may be in the range of 20 to 70% by weight of theentire material powders. If the proportion of the flat powder particlesis less than 20% by weight, then the proportion of copper segregatingtoward the surface decreases, and thus frictional resistance becomeslarge. On the other hand, if the proportion of the flat powder particlesis over 70% by weight, then the proportion of copper becomes too largeto obtain superior strength. Accordingly, by employing theabove-described range, the sliding component having reduced frictionalresistance as well as superior strength can be obtained. Morepreferably, the proportion of the flat powder particles may be in arange of from 20 to 40% by weight.

Still further, according to the above-described method, the averagevalue of the maximum projected areas of the flat powder particles may beat least three times as large as that of the maximum projected areas ofthe particles of the iron-based material powder. Due to such largedifference in the maximum projected area, segregation is easy to takeplace, facilitating each particle's flat surface of the flat powderparticles being disposed along a surface defining the surrounding of thefilling portion. By applying vibration or the like in that condition,the flat powder particles are allowed to be more easily disposed alongthe surface defining the surrounding of the filling portion so thatcopper is allowed to easily segregate on the surface of the greencompact.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart for explaining a method for manufacturing asliding component according to a preferred embodiment of the presentinvention;

FIG. 2 is a front view showing an iron-based material powder accordingto the preferred embodiment;

FIGS. 3A and 3B show a flat particle of copper-based material powderaccording to the preferred embodiment, wherein FIG. 3A is a side viewthereof, and FIG. 3B is a front view thereof;

FIG. 4 is an explanatory diagram showing a maximum projected areaaccording to the preferred embodiment;

FIG. 5 is a perspective view showing a bearing according to thepreferred embodiment;

FIG. 6 is a cross sectional view showing a mold according to thepreferred embodiment;

FIG. 7 is a partly enlarged cross sectional view showing a green compactaccording to the preferred embodiment; and

FIGS. 8A and 8B are explanatory diagrams schematically illustratingcolor pictures showing a surface of the sliding component for explaininga process for measuring a surface coverage of copper according to thepreferred embodiment, wherein FIG. 8A shows a surface condition asmeasured, and FIG. 8B shows that it is grid-coded using hatchings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Preferred embodiments of the present invention will now be explained indetail with reference to accompanying drawings. FIGS. 1 to 8 show anembodiment of the present invention.

First, a method for manufacturing a sliding component according to anembodiment of the present invention will now be explained. An iron-basedmaterial powder 1, a copper-based material powder 2 and a small amountof an other material powder 3 are mixed as materials in a predeterminedproportion (Step S1). For the iron-based material powder 1, a powdercomposed of substantially spherical and irregular particles such asatomized powder is used as shown in FIG. 2. For the copper-basedmaterial powder 2, an irregular-particle powder 2A and a flat powderparticles 2B are used as shown in FIGS. 2, 3A and 3B.

An iron or iron alloy powder is used as the iron-based material powder1, while copper or copper alloy powder is used as the copper-basedmaterial powder 2. Tin, carbon, phosphorus or zinc powder is used as theother material powder 3.

A preferable aspect ratio (diameter D/thickness T) of the flat powderparticles 2B is greater than or equal to 10, which is more preferably ina range of 20 to 50. A preferable average value of a maximum projectedarea M of the flat powder particles 2B is greater than that of a maximumprojected area m of the iron-based material powder 1, which is morepreferably three times as large as that of the maximum projected area m.Meanwhile, what is meant by the term “maximum projected area” herein isa maximum area for an object to occupy when the object is projected on aplane. Moreover, a preferable proportion of the flat powder particles 2Bin the entire materials is 20 to 70% by weight, which is more preferably20 to 40% by weight. The aspect ratio of the flat powder particles 2B isgreater than that of the iron-based material powder 1.

For instance, preferable materials may be comprised of 45 to 50% byweight of the copper material powder 2, 1 to 3% by weight of a tinmaterial powder serving as the other material powder 3, 0.2 to 0.7% byweight of a carbon material powder also serving as the other materialpowder 3, 0.2 to 0.6% by weight of a phosphorous material powder alsoserving as the other material powder 3, 1 to 3% by weight of a zincmaterial powder also serving as the other material powder 3, and theiron material powder that is the remaining material powder, serving asthe iron-based material powder 1. The ratio of the flat copper powder 2Bto the entire material powders is 20 to 40% by weight. Meanwhile, whenthe ratio of the flat copper powder 2B is 20 to 40% by weight, then theirregular-particle copper powder 2A will make up 15 to 30% by weight.

As shown in FIG. 5, a bearing 5 is formed essentially cylindrical, whilea sliding surface 51 of an essentially cylindrical shape, on which arotation shaft (not shown) as a rotation body rotates and slides, isformed on a center of the bearing 5. On longitudinally opposite ends ofthe sliding surface 51 are formed flat end faces 52, 53 disposedparallel to each other, while a peripheral surface 54 thereof is formedcylindrical.

FIG. 6 shows an example of a mold 11. This mold 11 employs a structurethat its top-to-bottom direction is aligned to an axial directionthereof (vertical axial pressing direction) and comprises: a die 12; acore rod 13, a lower punch 14; and an upper punch 15. The die 12 isformed into an essentially cylindrical shape with a hollow interior,while the core rod 13 that is formed into an essentiallycylindrical-pillar shape is coaxially disposed in the hollow interior ofthe die 12. The lower punch 14 is formed into an essentially cylindricalshape with a hollow interior and fitted from the bottom side of the mold11 into between the die 12 and the core rod 13 in a manner capable offreely moving up and down. Likewise, the upper punch 15 is formed intoan essentially cylindrical shape with a hollow interior, and removablyinserted from the top side of the mold 11 into between the die 12 andthe core rod 13 in a manner capable of freely moving up and down. Afilling portion 16 is formed inside the die 12 and between the core rod13 and the lower punch 14, while a peripheral inner surface of the die12 forms the aforesaid peripheral surface 54, an upper surface of thelower punch 14 forms the aforesaid end face 53, a lower surface of theupper punch 15 forms the end face 52, and a peripheral outer surface ofthe core rod 13 forms the sliding surface 51, respectively.

As shown in FIG. 6, the material powders 1, 2 and 3, which are mixedwith one another (Step S1), are filled into the filling portion 16.Then, vibration is applied to the mixed material powders (Step S2). Inthis case, an upper portion of the filling portion 16 is blocked off bythe upper punch 15, and then vibration of about 0.01-3 G is applied tothe filling portion 16 without pressing by the upper and lower punches14 and 15. When vibrated, the particles of flat powder particles 2B areallowed to segregate on the outer side within the filling portion 16,overlapped along the thickness direction thereof, while being gatheredin a manner that each particle is disposed so that its lengthwisedirection orthogonal to the thickness direction is aligned with alengthwise direction of the surface of the sliding component. Then, agreen compact 6 is formed by pressing the material powders 1, 2 and 3 inthe filling portion 16, using the upper and lower punches 15 and 14(Step S3). As shown in FIG. 7, it is to be noted that the green compact6 allows the flat copper powder 2B to be gathered toward the surface,and the ratio of the iron-based material powder 1 gradually increasestoward the inside thereof. By sintering the green compact 6 (Step S4)thus obtained, a bearing 5 as a sinter is formed.

Meanwhile, since each particle of the flat powder particles 2B has arelatively large flat surface, the flat powder particles 2B may besegregated on the outer side in the filling portion 16 by generatingstatic electricity on a surface of the mold 11 surrounding the fillingportion 16 or by applying magnetic force thereto.

Surface coverage of copper of not less than 90 percent was obtained whenthat of the bearing 5 produced under the following condition wasmeasured: Namely, the material powders 1, 2 and 3 were composed of: 48%by weight of the copper material powder 2; 2% by weight of the tinmaterial powder 3; 0.5% by weight of the carbon material powder 3; 0.4%by weight of the phosphorus material powder 3; 2% by weight of the zincmaterial powder 3; and the iron-based material powder 1 as the remainingmaterial powder, in which the ratio of the flat copper powder 2B to theentire materials was 30% by weight. The material powders 1, 2 and 3 thuscomposed were filled into the filling portion 16, subjected to about0.05 to 0.1 G vibration for 0.5 second, then pressurized to thereby formthe green compact 6, and sintered to obtain the bearing 5.

The above-described surface coverage of copper is measured by thefollowing procedures; taking a color picture of the surface of thebearing 5 (magnification: ×100); laying a frame of a predetermined 2mm-square grid type tracing paper on the color picture; and calculatinga ratio of an area of a copper region. An example thereof will now beexplained with reference to FIGS. 8A and 8B. FIG. 8A shows a graphicalrepresentation of the color picture of the surface of the bearing 5 onwhich the copper region 11 of copper or copper alloy, an iron region 12of iron or iron alloy and a pore region 13 appear. A plurality of grids22 arranged in rows are formed on a predetermined region of a frame 21comprising a clear board or the like. Both FIGS. 8A and 8B show theframe 21 having 10-by-10 grids as an example. Among the regions 11, 12and 13, the one that occupies the largest area in each grid 22 iscounted as one corresponding to each grid 22, and thus the surfacecoverage by the copper region 11 except the pore region 13 iscalculated. For illustrative purposes, FIG. 8B shows that these regions11, 12 and 13 are grid-coded using hatchings, in which the numbers ofthe grids 22 allocated to each region is 84 for the copper region 11, 6for the iron region 12, and 9 for the pore region 13. Since the surfacecoverage of copper should be calculated excepting the pore region 13from consideration, it is given by the following equation:84/91×100=92.3%.

When the surface coverage of copper in the sliding surface 51 was 100%,frictional resistance thereof indicated the lowest value, and a noisewas not generated in an experiment in which the rotation of the rotationshaft was initiated at the temperature of −40° C. Similar result wasobtained up to about 90% surface coverage of copper. However, if theratio of the copper-based material powder is over 70% by weight, thenstrength will be decreased even though the surface coverage of copper is100%, and thus the ratio of the copper material powder 2 to the entirematerial powders were set in the range of from 20 to 70% by weight.

As described above, there is provided the bearing 5 as the slidingcomponent according to the present embodiment, the sliding componentbeing formed by: filling the iron-and copper-based material powders 1and 2 into the filling portion 16 of the mold 11; compacting thematerial powders 1 and 2 so as to form the green compact 6; and thensintering the green compact 6, wherein the copper-based material powder2 contains the flat powder particles 2B of copper or copper alloy; theaverage value of the maximum projected areas M of the flat powderparticles 2B is larger than that of the maximum projected areas m of theparticles of the iron-based material powder 1; and copper is allowed tosegregate on the surface.

Thus, by filling the flat powder particles 2B into the filling portion16 of the mold together with other material powder 1, allowing the flatpowder particles 2B to segregate on the surface of the slidingcomponent, using vibration, electrostatic force, magnetic force or thelike, there can be provided the bearing 5 having its surface coveredwith copper, generating a concentration gradient in which thecopper-to-iron ratio thereof decreases from the surface of the slidingcomponent toward the inside thereof while increasing the ratio of ironto copper.

Accordingly, as the rotation body slides on the sliding surface 51covered with copper, frictional resistance between the rotation body andthe sliding surface 51 is reduced, and thus a smooth rotation isrealized, while a predetermined strength as well as durability can beobtained by virtue of iron. Moreover, according to this structure, eventhough the sliding surface 51 wears due to the sliding by the rotationbody, the sliding surface 51 can maintain superior durability sincecopper is contained at the predetermined ratios under the worn slidingsurface 51.

Further, according to this embodiment, the flat powder particles 2B havea larger aspect ratio than the particles of the iron-based materialpowder 1, allowing copper to segregate on the surface.

Furthermore, since the surface coverage of copper in the sliding surface51 serving as the sliding portion is greater than or equal to 60%,frictional resistance of the sliding surface 51 can be drasticallydecreased. More preferably, the surface coverage of copper in thesliding surface 51 may be not less than 90%.

Still further, in this embodiment, the sliding portion is defined by thecylindrical sliding surface 51, thus providing the bearing 5rotationally supporting the rotation shaft by this sliding surface 51.

Moreover, according to this embodiment, in the manufacture method of thebearing 5 as the sliding component, comprising the steps of: fillingiron-based material powder 1 and copper-based material powder 2 into thefilling portion 16 of the mold 11; compacting the iron and copper-basedmaterial powders 1 and 2 so as to form the green compact 6; andsintering the green compact 6, wherein: the copper-based material powder2 contains flat powder particles 2B of copper or copper alloy; and theaverage value of the maximum projected areas M of the flat powderparticles 2B is larger than that of the maximum projected areas m of theparticles of the iron-based material powder 1; and the flat powderparticles 2B in the filling portion 16 is allowed to segregate on thesurface of the green compact 6, whereby the bearing 5 formed from thegreen compact 6 can have reduced frictional coefficient as well assuperior durability.

Moreover, according to this embodiment, the flat powder particles 2Bhave a larger aspect ratio than the particles of the iron-based materialpowder 1, and thus the flat powder particles 2B in the filling portion16 can be allowed to segregate on the surface of the green compact 6.

Further, as the aspect ratio of the flat powder particles 2B is greaterthan or equal to 10, the flat powder particles 2B can be successfullysegregated on the sliding surface 51 by applying vibration, staticelectricity, magnetic force or the like, and thus the bearing 5 havingthe sliding surface 51 with high copper concentration can be obtained.Meanwhile, the aspect ratio of the flat powder particles 2B may be morepreferably in the range of 20 to 50.

Still further, as the ratio of the flat powder particles 2B to theentire material powders is in the range of from 20 to 70% by weight, thebearing 5 having small frictional resistance as well as superiorstrength can be produced. Meanwhile, the ratio of the flat powderparticles 2B may be more preferably in a range of from 20 to 40% byweight.

Moreover, according to this embodiment, the average value of the maximumprojected areas M of the flat powder particles 2B is at least 3 timeslarger than that of the maximum projected areas m of the particles ofthe iron-based material powder 1. As the difference in maximum projectedarea between the flat powder particles 2B and the particles of theiron-based material powder 1 is large, the segregation of the flatpowder particles 2B is easy to take place, while each particle of thematerial powder 1 is brought into a condition contacting the surface ofeach of the flat powder particles 2B in the filling portion 16, wherebyeach flat surface of the flat powder particles 2B can be easily disposedalong the surface surrounding the filling portion 16 (i.e., the surfacedefined by the surfaces of the die 12, the core rod 13, the punches 14and 15 all forming the filling portion 16), and thus copper is easilysegregated on the surface (sliding surface 51) of the green compact 6 byapplying vibration in this condition.

The above-described embodiments are intended to illustrate the presentinvention, not to limit the scope of the present invention. Variousembodiments and changes may be made thereonto without departing from thebroad spirit and scope of the invention. For example, the flat powderparticles 2B may be one of a bar-like shape. In that case, aspect ratiothereof is expressed as a ratio of its length to its diameter.Alternatively, the flat powder particles may take a square-tabularshape, and in that case, aspect ratio thereof is to be expressed as aratio of a length of its diagonal line to its thickness. Further, thecopper-based material powder 2 may be composed of the flat powderparticles 2B only.

1. A sliding component comprising: a sintered green compact formed fromcompacted iron-based material powder and copper-based material powder,wherein said copper-based material powder contains flat powder particlesof copper or copper alloy; an average value of maximum projected areasof the flat powder particles is larger than that of maximum projectedareas of iron-based material powder particles; and copper is segregatedon a surface of said sliding component.
 2. The sliding componentaccording to claim 1, further comprising: a sliding portion having asurface coverage of copper greater than or equal to 60%.
 3. The slidingcomponent according to claim 2, wherein the surface coverage of copperis greater than or equal to 90%.
 4. The sliding component according toclaim 1, wherein said sliding component generates a concentrationgradient in which a copper-to-iron ratio thereof decreases from thesurface of the sliding component toward an inside thereof whileincreasing the ratio of iron to copper.
 5. The sliding componentaccording to claim 2, wherein said one surface is a sliding surfaceformed in a cylindrical shape.
 6. A method for manufacturing a slidingcomponent, comprising the steps of: filling an iron-based materialpowder and a copper-based material powder into a filling portion of amold; compacting said iron-based material powder and copper-basedmaterial powder so as to form a green compact; and sintering said greencompact, wherein said copper-based material powder contains flat powderparticles of copper or copper alloy; an average value of maximumprojected areas of the flat powder particles is larger than that ofmaximum projected areas of iron-based material powder particles; andsaid flat powder particles in the filling portion are segregated on asurface of said green compact.
 7. he method for manufacturing a slidingcomponent according to claim 6, wherein the aspect ratio of each flatpowder particle is greater than or equal to
 10. 8. The method formanufacturing a sliding component according to claim 7, wherein theaspect ratio of each flat powder particle is in a range of 20 to
 50. 9.The method for manufacturing a sliding component according to claim 7,further including the step of: segregating said flat powder particlestoward the surface of said sliding component by applying vibration tosaid iron-based material powder and copper-based material powder filledin the filling portion of the mold.
 10. The method for manufacturing asliding component according to claim 6, wherein a ratio of said flatpowder particles to the entire material powders is in a range of 20 to70% by weight.
 11. The method for manufacturing a sliding componentaccording to claim 7, wherein a ratio of said flat powder particles tothe entire material powders is in a range of 20 to 70% by weight. 12.The method for manufacturing a sliding component according to claim 10,wherein the ratio of said flat powder particles to the entire materialpowders is in a range of 20 to 40% by weight.
 13. The method formanufacturing a sliding component according to claim 6, wherein theaverage value of the maximum projected areas of the flat powderparticles is at least 3 times as large as that of the maximum projectedareas of the iron-based material powder particles.
 14. The method formanufacturing a sliding component according to claim 7, wherein theaverage value of the maximum projected areas of the flat powderparticles is at least 3 times as large as that of the maximum projectedareas of the iron-based material powder particles.
 15. The method formanufacturing a sliding component according to claim 10, wherein theaverage value of the maximum projected areas of the flat powderparticles is at least 3 times as large as that of the maximum projectedareas of the iron-based material powder particles.